A typical transformer has a primary winding (hereinafter sometimes “primary”) magnetically coupled to a secondary winding (hereinafter sometimes “secondary”). The magnetic Coupling is usually accomplished with one or more magnetic cores about which the primary and secondary are wound. In a so-called “ideal” transformer (that is, one which neither stores nor dissipates energy, has unity coupling coefficients, and has pure inductances of infinite value), current flowing in the primary induces a current flow in the secondary that is equal to the current in the primary times the ratio of the number of turns of the primary to the number of turns of the secondary. In real, non-ideal transformers, losses arise from factors such as winding resistances, magnetic flux changes, unequal magnetic flux sharing between the primary and secondary, eddy currents, loads coupled in circuit with the secondary, and other factors. The cumulative result of all these factors is that the current flowing in the secondary is not related to the current flowing in the primary by the turns ratio.
Precision measurement devices, such as watt-hour meters, have transformers and associated circuitry that senses current flowing from generating equipment of, for example, an electric utility, through the measurement device to a customer. Increasing the accuracy of such measurement devices results in more accurate billing of customers for their consumption of electricity. Transformers having electrical circuitry that compensates for the non-ideal nature of the current relationship between current flow in the primary and current flow in the secondary are known. See, for example, U.S. Pat. Nos. 3,153,758; 3,500,171; 3,534,247; 4,841,236; 5,276,394; and 5,307,008. This listing does not constitute a representation that a thorough search of all relevant prior art has been conducted, or that there is no more relevant prior art than that listed, or that the prior art listed is material to patentability. Nor should any such representation be inferred.